ValueTuple not working in Razor views with MVC 5

I have an ASP.NET MVC 5 project in Visual Studio 2017 and after successfully adding C# 7 support (which has worked for me so far), I tried using tuples in my Razor views, but I got a surprising error message:

I suspect that's the problem. My guess is that even though you're targeting .NET 4.5.2, you're running on a .NET 4.7 system, and that includes System.ValueTuple in mscorlib.

I suggest you remove the package dependency on the System.ValueTuple package, and update your target framework to .NET 4.7 (as you seem to be running on that anyway)... if that change doesn't break other things, of course...